基于铜基空穴传输材料的低铅/非铅钙钛矿太阳能电池研究

Perovskite solar cells (PSCs) have received tremendous attention in both academia and industry due to their high power conversion efficiencies (PCEs) and easy processing. PSCs face two main challenges towards realizing its practical application: the first one is the instability of perovskite materials and devices, the second one is the toxicity of Pb. The study of lead-free perovskite materials is mainly focused on the Sn-based perovskite. However, the PCE of Sn-based perovskite solar cells are generally low. The root cause of this phenomenon is the energy loss of solar cells, which severely limits the room for the open-circuit voltage (Voc). Therefore, the reasonable design of device structure is of great significance to further improve the PCE of Sn-based solar cells. Inorganic p-type Cu-based semiconductor is supposed to be a promising alternative hole-transporting material, due to its low cost, solution processability and environment-friendly nature. With the aim to investigate how to solve the low Voc of Sn-based perovskite solar cell, we systematically design and prepare a series of Cu-based hole-transporting materials with proper energy level, excellent stability and high hole mobility. The energy-level matching rule between hole-transport layer and Sn-based perovskite active layer, as well as the charge transporting mechanism, is deeply explored. The key factors influencing the Voc, PCE and stability of Sn-based perovskite solar cells are clarified, providing theoretical support for the development of Sn-based perovskite solar cells with high-efficiency, good stability and low toxicity.

钙钛矿太阳能电池由于具有高光伏效率和易加工制备等优点备受学术界和工业界的关注。钙钛矿太阳能电池要实现实用化还面临两大挑战：1. 材料和器件的稳定性问题；2. 铅毒性问题。目前，非铅钙钛矿材料的研究主要集中在锡基钙钛矿上。但锡基钙钛矿太阳能电池的光伏效率普遍偏低，其根本原因在于电池内部具有较高的能量损失，严重限制了其开路电压的提升。因此，合理设计器件结构对进一步提高锡基钙钛矿电池的光伏效率具有重要意义。铜基无机p型半导体具有成本低廉、可溶液合成、环境友好等优点，被认为是具有潜力的空穴传输材料。本项目拟围绕如何解决锡基钙钛矿电池中开路电压低这一核心问题，系统设计和制备一系列具有合适能级、优异稳定性和高空穴迁移率的铜基空穴传输材料，并探究它们与锡基钙钛矿活性层的能级匹配规律和电荷输运机理，厘清影响电池开路电压、光伏效率和稳定性的关键因素，为高效、稳定和低毒锡基钙钛矿电池的发展提供理论支撑。

钙钛矿太阳能电池在过去十年里得到了飞速的发展，其效率已经逼近传统硅基太阳能电池。但是目前钙钛矿电池里包含的重金属铅元素限制了其大规模商业化应用。因此构建高性能无铅或少铅钙钛矿太阳能电池迫在眉睫。但少铅钙钛矿材料的能级结构与传统有机空穴传输层spiro-OMeTAD的匹配性较差，寻找其它空穴传输材料来制备少铅钙钛矿电池具有重要意义。在众多空穴传输材料里，铜基无机空穴传输材料因其具有成本低廉，稳定性好，空穴迁移率高等优点，被认为是下一代空穴传输材料的重要候选者之一。本项目以构筑高性能铜基空穴传输材料的钙钛矿电池为目标，从铜基p型半导体纳米颗粒的可控制备出发，围绕其成膜过程，电学性能优化和其作为空穴传输层在电池中的电荷输运机制等方面展开研究，项目研究内容如下：1. 分别采用室温溶液法和微乳液法成功制备硫化铜和碘化亚铜纳米材料，通过调控硫脲和十六烷基三甲基溴化铵的用量，并结合XRD和SEM表征技术，证实了我们获得了较高纯度且尺寸较小的硫化铜和碘化亚铜纳米颗粒；最后基于铜基空穴修饰层的钙钛矿器件效率分别达到了13.91%和18.42%。2. 通过在传统有机空穴传输材料spiro-OMeTAD中掺入一系列氧化剂（I2，K2S2O8，K3[Fe(CN)6]和DDQ），不仅缩短了spiro-OMeTAD的氧化时间，而且提高了spiro-OMeTAD空穴传输层的导电性；光电测试结果表明基于氧化剂掺杂的spiro-OMeTAD空穴传输层器件的光电效率都得到了一定幅度的提升（19.69%，I2；20.00%，K2S2O8；20.84%，K3[Fe(CN)6]；21.12%，DDQ）；此外，掺杂后的电池迟滞现象减小，稳定性能也得到了改善。这一系列项目成果对未来钙钛矿太阳能电池中空穴传输层的设计合成提供了一定的理论支撑和技术指导。